To better understand the situation: You can generally see the Pixel as connected device from Windows, when connected via USB?
Other quick, random guess: Do you use the original USB-C cable, that came with the Pixel?
I had odd connectivity effects in in the past as well. Had to learn that even apparently high quality USB-C cables did not necessarily fit my Pixels in the optimal way. They can ofc. The original cable supplied might just eliminate one potential source of errors. So I was wondering about that aspect.